Issue with my refrig: Frost on back of Freezer. No air (cool or otherwise) really coming through to the food side unless Freezer is really cold, but then only makes the Frost thicker. Is it the motherboard or the heater or the thermostat that I should replace?
You can check the defrost limiter to see if it has continuity. If it does not have continuity then you would not need to change it out. You will also want to check the defrost thermistor for resistance. The resistance values should be as follows, 42.5K at 0 degrees, 14.4k at 37 degrees and 5K ohms at 77 degrees. If not within range then it would need to be replaced. If it checks good then also check the defrost heater for continuity. If no continuity then replace and if good with continuity and all other components check ok then you would need a new main control board. You can test this with a multi-meter TJMA-DMT3. Here is a link on how to use a multi-meter. http://forum.appliancepartspros.com/oven-repair-including-ranges-cooktops/4810-how-check-continuity-ohmmeter.html
How do I install a single defrost heater element with a dual element heater?
You would install the heater the same way as the original heater by screwing to the bracket. What changes is where the wire on the left side goes. The kit comes with a yellow wire that if the original blue wire is too short you can cut the connector off and splice the yellow wire to it to make it longer. This will allow the wire to go across where the other wire comes down the right side of the evaporator and connect to the element. You can connect either wire to the terminals and there is a jumper on the other end of the heater connecting them together.